Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 32,533	$ 29,726
Short-term marketable securities	62,410	73,934
Accounts receivable (net of allowance for doubtful accounts; 2015—$3,988, 2014—$3,628)	37,164	34,916
Prepaid expenses and other current assets	10,843	9,944
Total current assets	142,950	148,520
Property and equipment, net	39,746	21,860
Other assets	1,921	15,541
Total assets	184,617	185,921
Current liabilities:
Accounts payable	8,585	6,987
Accrued compensation and employee benefits	22,239	17,708
Accrued license fees	2,287	2,656
Accrued expenses and other current liabilities	8,922	10,444
Deferred revenues	431	335
Other current liabilities	208	208
Total current liabilities	42,672	38,338
Other liabilities	$ 2,410	$ 2,070
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.0001 par value, 5,000,000 shares authorized, no shares issued and outstanding
Common stock, $0.0001 par value; 100,000,000 shares authorized, 33,861,759 and 32,969,232 shares issued and 32,800,428 and 31,911,901 shares outstanding at December 31, 2015 and 2014, respectively	$ 3	$ 3
Additional paid- in capital	395,059	370,496
Accumulated other comprehensive income (loss), net	2,752	(15)
Accumulated deficit	(228,169)	(194,861)
Treasury stock, at cost, 1,061,331 shares at December 31, 2015 and 2014	(30,110)	(30,110)
Total stockholders' equity	139,535	145,513
Total liabilities and stockholders' equity	$ 184,617	$ 185,921